A n interactive computer aid for designing log/ca/networks representing air-traffic-control systems is described. Parallel activity streams can be described, the network functions being represented by CORAL procedures and by hierarchical sets of subnetworks. Dynamic visual checks can be made of system logic, and system behaviour can be simulated. Some current limitations to the use of networks to describe man-machine systems generally are discussed, and ways of usefully extending the work are suggested.
Air-traffic control has come to depend increasingly on computers for the preparation and display of aircraft information. Several of the most recent proposals for systems also include a degree of automatic problem solving as an online scheduling aid to operational airtraffic controllers. Before such systems are introduced into service, it is normal for them to be exposed to controller evaluations. This is done by mounting expensive and elaborate evaluation exercises on mockups which, in some ways, are analogous to aircraft flight simulators. Such evaluations have, in the past, proved to be very useful, and will, no doubt, continue to be used as a preliminary to the introduction of new techniques into operational services. However, between the initial design of new systems and such evaluation exercises, there appears to be room for a cheaper and more convenient evaluation facility. Such a facility would allow a wider range of organizations and control strategies to be quantitatively compared before the more expensive, and therefore more limited, evaluation exercises were mounted.
To try to satisfy this requirement, an interactive system simulation facility has been designed for use on a MOD ] computer running under MINOS. It is written in CORAL 66, and allows system descriptions to be entered rapidly into the machine without there being a need to know a complex simulation language. By giving suitable responses to prompts, a network description of a proposed system can be generated and displayed on a graphics terminal. The models built up can then be exercized and their performance evaluated.
CHOICE OF SYMBOLISM
Although no formal language appears to exist specifically for representing the sequences of activities performed by Royal Signals and Radar Establishment, St. Andrews Road, Great